So would you want it to keep the same custom ratio too, or enlarge the crop to keep all available pixels?

There are occasions when I've cropped a photo smaller, rotated it, and then wanted to reset the crop without resetting the rotation.

I'd imagined a button near the reset crop, so perhaps it could have a modifier toggle to switch between maximizing retained pixels with rotation and maximizing at the custom ratio - or perhaps it would automatically keep the custom ratio if it was locked.

I would want the latter: enlarge crop to keep all available pixels - OK if aspect ratio changes.

Now that you mention it, I think I see why it is the way it is: aspect ratio is being maintained upon rotation - whether locked or unlocked. Perhaps it could be as simple as maximizing width if ratio is unlocked.

PS - I like your idea about being able to reset the crop without resetting rotation.